JPH0773601A - Equipment and method for checking formatted block on magnetic tape and checking validity - Google Patents

Abstract

PURPOSE: To make it possible to easily detect formatted blocks and decide their validity by coping with a format entity pattern by using a programmable corresponding threshold value in each required mode. CONSTITUTION: In a read-only (R) mode and a read-while-write(RWW) mode, PLL 40 of a block/validity detection system 36 detects a synchronous character, and at the same time, a burst detection logic circuit 42 detects an interblock gap (IBG), a synchronous burst, by using a threshold value of a parameter/ threshold circuit 48. These detection patterns are decided as valid for threshold values higher than the detected ones from the circuit 48 by the individual logic circuits 64-66 of synchronization, IBG, and burst qualification, and when the validity are not satisfied, a status message requesting for Θ-block rewrite is generated, and it is possible to easily detect blocks and decide their validity.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates generally to recording and retrieving digital information on magnetic tape, and more particularly to reading data from and writing data to the magnetic tape. It relates to the detection and validation of formatted magnetic tape data during transfer operations.

[0002]

The standard for magnetic tape drives for recording digital information on moving magnetic tape media is to record data on one or more tracks (channels) in a series of formatted blocks. Is intended. Each block is a tape drive controller for monitoring and managing the flow of information to and from the magnetic tape and for controlling the magnetic heads and other hardware used during read and write operations. Format entity used by the.

The formatting entity relevant to the present invention is the inter-block gap, ie the boundary area between each block known as the IBG and the entity within the block that contains the acquired burst pattern, the intermediate burst pattern, and the byte sync character. Is included. reading·
When associated with a write operation, a conventional tape drive controller utilizes these format entities to obtain basic timing and control information. For example, the presence of an inter-block gap informs the controller that a formatted block is approaching, and the controller should next expect an acquisition burst indicating that the block has arrived. Let us know. When an acquisition burst is sensed, the track read circuit bit synchronization (clocking) is initiated and the controller begins waiting for a byte sync character. When a sufficient number of byte sync characters are detected, the track read circuit is byte synced and a data transfer operation within the formatted block is initiated. Subsequent formatting entities in the block help maintain bit and byte synchronization as the block is processed.

In some prior art tape drives, the detection and validation of formatted blocks during read / write data transfer operations is performed by microcode routines executed by the tape drive controller. For example, microcode has been used to detect interblock gaps by sampling a register containing the bit pattern information reported by the magnetic head and detection circuitry. The microcode responds to the interrupt from the hardware when the interblock gap pattern is complete. The microcode then asks to poll another register to determine if a burst acquisition has occurred. If burst acquisition does not occur after the specified time,
Microcode must do error recovery.
If a burst acquisition occurs and the hardware detects a start sync character, another interrupt is generated to inform the microcode that the data is now ready for processing. However, in many cases, the microcode is overloaded so that it does not have the time to respond to the interrupt, and thus requires polling other registers to determine when the start sync character was set. If the starting sync character is not detected within some specified time, the microcode must call the error recovery routine again. If a sufficiently high priority interrupt occurs during this process, an entire block may be lost, thus requiring repositioning and read / write retries. Therefore, it is desirable to have a magnetic tape data storage device that does not require extensive use of microcode resources to perform block detection and validation operations.

In addition, it is desirable to provide programmability in the detection and validation of formatted data blocks for multiple modes of operation of tape drives. Typical operation modes of the magnetic tape storage device include "read only" and "playback during recording". In the context of the present invention, "detection" refers to sensing a format entity in any mode using a detection threshold criterion. “Validation” refers to sensing a format entity in “play-on-record” using a validation threshold criterion to validate what was written. In a conventional tape drive,
Inter-block gaps, acquisition bursts, and sync characters are programmed to detect in various ways in "Play on Record" rather than in "Read Only".
A higher detection criterion is required for "playback on record" than "read only", and the higher "playback on record" detection criterion is also used as a write validity criterion. This ensures that a satisfactory data recording is maintained and allows write retries if the recorded data does not meet the more stringent criteria applicable to the "play on record" mode. However, the need to use high validation criteria during "playback on record" also enhances the "playback on record" detection criteria. This is because the two criteria are the same (ie "play on record" detection and plausibility check).

The disadvantage of using pre-programmed non-uniform detection criteria in the "read-only" and "play-on-record" modes is that the block format entity detects different parts of the tape in each mode. That is what is done. For example, a low "read only" criterion may result in detection of an acquired burst before burst detection occurs in "playback on record" mode. The acquisition burst is used to initiate frequency lock in a phase locked loop (PLL) circuit for bit synchronization. If different criteria are used to detect the acquisition burst in "read-only" mode than when a block is written, different parts of the starting burst may be used for clock acquisition, And if that part of the tape is bad, the clock may not be able to lock onto the data at all. It is preferable to start clock acquisition at the same location on the tape, regardless of mode.

Another drawback resulting from the use of pre-programmed non-uniform detection criteria in various modes of tape drive operation occurs when write skips are made. A write skip causes a write retry without rewinding the tape as a result of a data write error. The tape drive finishes writing blocks in a pipeline and then performs a write retry. Writing errors can be caused by debris causing the tape to lift momentarily from the writing head. The microcode produces a write error because the read circuit does not detect the block using the "play-on-write" threshold criteria. In some cases, the portion of the tape that causes the write error contains a block of old data. However, because write retries occur downstream, the old data blocks remain on the tape and are read (using the less stringent "read-only" criteria) during subsequent tape reads.
As a result, block ID sequence errors or data integrity errors may occur.

Therefore, by implementing a formatted block detection and validation operation in hardware, and by using programmable detection and validation criteria over multiple operating modes of the tape drive, There is a clear need in the art for a magnetic tape drive that overcomes the disadvantages of. Hardware-based systems will remove much of the indirect cost of block detection and validation from the controller microprocessor. Programmable detection and validation criteria provide different detection criteria and different validity under special circumstances if they allow nominally uniform detection criteria to be applied across multiple operating modes. It also makes it possible to use inspection criteria.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an apparatus and method for detecting and validating formatted blocks during read / write data operations in magnetic tape data storage systems. is there.

[0010]

A magnetic tape data storage system reads and writes data on a magnetic tape medium in a plurality of modes, including a "read only (R)" mode or a "playback on record (RWW)" mode. Contains component functionality for writing data to it. Note that the data is arranged in one or more tracks in a series of formatted blocks. In the preferred embodiment of the invention, the detection and validation of the formatted block uses first and second programmable detection thresholds that are the same or substantially the same in both R and RWW modes. A block acquisition burst, a sync character, or at least one format entity representative of any other desired format entity. In addition, a plausibility check decision is made in RWW mode whether the detection of the format entity meets an RWW error threshold greater than the first and second programmable detection thresholds.
If the RWW error threshold is not met, a message is generated indicating that a write retry may be needed. In this way, the detection of different format entities is achieved uniformly in R and RWW modes, but in RWW mode, provisions are made to apply more stringent threshold criteria for write validation. Is done.

[0011]

【Example】

A. Tape Formatting Referring to FIG. 1, a magnetic tape medium 2 for recording one or more parallel data tracks (not shown) oriented horizontally with respect to that figure is shown. Data recording can be unidirectional or bidirectional. The data is arranged in formatted serial blocks. In FIG. 1, two of the blocks are partially indicated by reference numerals 4 and 6. Formatted blocks 4 and 6 are separated by an inter-block gap (IBG) 8. Formatted blocks 4 and 6, as well as IBG8, contain data patterns that represent the formatting entities used to detect and validate the formatted blocks during read and write data transfer operations. . More specifically, the format entity provides the information to obtain bit sync and byte sync on each simultaneously recorded data track.

Formatting entities relevant to this application include acquisition bursts in physical blocks, resync bursts, and sync characters, and also the IBG itself. Formatted blocks 4 and 6 include acquisition bursts 10 and 12, respectively, which acquisition burst 10 is located at the end of block 4 and acquisition burst 12 is located at the beginning of block 6. Also, formatted blocks 4 and 6 contain multiple resync bursts, two of which are shown in FIG. 1 as reference numbers 14 and 16. Adjacent to each acquisition burst and sync burst is one or more sync characters. Acquisition bursts 10 and 12 are bounded by sync characters 18 and 20, respectively. Resync burst 14 in formatted block 4 contains a pair of sync characters 22 and 2
Bounded by four. The resync burst 16 in the formatted block 6 is bounded by a pair of resync characters 26 and 28.

Both acquisition bursts and resync bursts are used to enable frequency and bit synchronization of the track clocking circuitry used to read and write data on the tape. They are formed by repeating a pattern of letters. The acquisition burst is preferably longer than the synchronization burst. They occur at the beginning and end of each physical block, while resync bursts occur between the ends of one physical block. The acquisition burst is designed to allow the read clocks for all currently read blocks to acquire bit synchronization for that data at the same time. The length of the acquisition burst depends on the maximum amount of skew and other factors across the tape so that all tracks receive the acquisition burst at the same time and a common clock component is used to obtain track width bit synchronization. Dependent. Resync bursts are provided to allow the individual track read clocks to reacquire bit sync within the physical block. Not all tracks need to read the resync burst at the same time because they are designed to allow individual tracks to be resynced. Therefore, the resync burst need not be as wide as the acquisition burst.

The sync character is used to obtain the byte sync of the detection circuit to the data boundary. They allow the controller to verify that a given track is character sync, or allow the track to get character sync if it is not. The sync character is placed after the first acquisition burst, before the last acquisition burst, and before and after each resync burst. Typically, sync characters are characters that have a single encoded value. Byte sync is obtained over those tracks when the first sync character is encountered following the first acquisition burst. Alignment is obtained by knowing when each cooperating track encounters one sync character and receiving subsequent data bytes in the proper order.

The IBG 8 is an area where host data is not recorded. Preferably, the IBGs are encoded with a repeating pattern of low frequency data other than a run length limited (RLL) encoding scheme for host data. For example, if the (1,7) RLL coding scheme is used, I
BG is a low frequency other than RLL coding system "1000000001
00000000 .... "can be coded with a data pattern, which is typically in contrast to acquisition bursts and resync bursts with high frequency data patterns in the highest frequency RLL coding scheme. Yes, for example
For the (1,7) RLL coding scheme, the acquisition burst and the resynchronization burst can be coded with a repeating "101010 ..." Data pattern.

IBG8 is typically much longer than acquisition and resync bursts. It has a write append (ap) to prevent the destruction of previously written data.
gives the area where the pends) are started. Furthermore, IBG
Provides a formatting entity with acquisition bursts, resync bursts, and sync characters for use in obtaining basic timing and control information.

B. Process Overview In the preferred embodiment of the present invention, in a multi-track block during read data flow (RDF) operation,
A comprehensive method is provided to detect and validate the "start of block (BOB)" and the "end of block (EOB)" (for backward data read). The method is such that when a block is subsequently read by using a "play-on-record (RWW)" threshold to verify proper margin while writing IBG, burst, and sync character markers, the BOB
Ensure successful detection and validation of

RD is the presence of blocks on the tape
Three events must occur for F to make a decision. First, the IBG must be detected in order to distinguish the expected head burst from the resync burst. Second, to give the PLL acquisition time faster and to open the window for the detection of the first sync character,
The first burst must be detected. Third, most tracks must detect sync character markers in order to set byte sync. These format entities must be validated in RWW mode.

To determine the transition from the IBG to the first burst, the IBG must first be detected.
IBG detection requires most tracks to detect a specified number of consecutive IBG intervals when searching for an IBG. Not all tracks need to detect the pattern, nor do individual tracks need to detect it at the same time. However, when writing the IBG pattern (during RWW), for validation purposes, all tracks, or at least substantially most of them, detect more consecutive IBG intervals than are needed for detection. RDF confirms that

Three interval count values associated with the IBG are programmable. These are the number of consecutive intervals that the IBG needs to be detected during "read-only" operation, the number that must be detected during RWW operation, and the RWW error threshold used for validation. In most cases, the first two count values are equal or at least substantially equal. The RWW error threshold count is preferably "read only" or RWW.
Greater than either of the threshold counts and good I needed to avoid write retries while in RWW mode.
Define the minimum length of the BG pattern. An example of three interval count thresholds for IBG detection and validation is 8, 8 and 16.

The point at which it is detected is not critical because the IBG is relatively long and is a pattern other than RLL code. When a track determines that the required number of consecutive IBG intervals has been detected, the IB
The G detect latch is set. By definition, an IBG has been detected if most tracks have their IBG detection latch set. Two IBG detection thresholds are used and they are programmable. These are the minimum number of IBG detection signals required to configure the IBG during "read only" operation and the number required during RWW operation. In most cases, the two thresholds are equal. I
An example of the BG detection threshold is 12 out of 16 tracks.

Another latch, IBGERR, is set first and it clears only if the number of consecutive IBG intervals detected in each of those tracks is equal to or exceeds the more stringent RWW error threshold. To be done. This latch is used to indicate to the microcode that the block should be rewritten with the intention of writing more detectable IBGs.

Conveniently, if RDF successfully reads a block, the IB that follows that block.
G is implied and the data flow is the required continuous I
IBG detection can be mitigated by reducing the number of BG intervals (eg, up to half).
This relaxation of the detection criteria increases the probability that an IBG will be detected, but it requires confirming the position of the read head between blocks. Once the IBG-burst transition is detected, the IBG detection criterion is returned to the non-relaxed value. Similarly, a higher I while one block is being read.
The BG threshold (HOTIBG) can be set (eg increased by half). This threshold anticipates that the block being read may have been partially overwritten by another block. Its higher HOTIBG
The threshold ensures that only true IBGs are detected before determining that a new block has been encountered. Once the end of block (EOB) is reached, HOTIBG is relaxed and the nominal IBG threshold is restored. IBG
The "read-only" and RWW interval count thresholds can be changed, but the RBG is sufficiently robust in all tracks to ensure subsequent detection.
The RWW error criteria for clearing the IBG latch is not changed to provide for WW operation.

The parameters that determine the presence of a burst are:
Basically the same as that used for the IBG decision. The burst detect latch is set when a track determines that the required number of consecutive burst intervals has been detected. If most tracks have their burst detect latch set, then by definition that burst has been detected. Three programmable burst interval count values and two programmable track thresholds are provided. Again, the same or substantially the same number of consecutive burst intervals are typically used for detection in "read only" and RWW modes. The burst RWW error threshold for consecutive intervals is used to validate that the first part of the leading burst is robust in RWW mode. An example of three interval count thresholds for burst detection and validation is 8, 8 and 16. To determine that most tracks are currently trying to detect a burst pattern, track voting (v
oating) is used. An example of a burst qualification threshold for both "read only" mode and RWW mode is 12 of 16 tracks.

Conveniently, when the IBG is detected, the first burst is the expected next pattern, so the data flow relaxes the criteria for detecting the burst (eg, only half). This increases the probability that the leading burst will be detected early, while it increases the probability that the clock acquisition will be completed in that burst.

After that, when the sync character is detected,
The criteria for burst detection are restored to their original values. This allows RDF to preferably distinguish subsequent resync bursts from burst-like intervals in the data.

Global detection and validation of sync characters is controlled by three programmable qualification thresholds.
The first is the number of tracks that detected the sync character marker to confirm the detection during "read only" operation. The second is the number of tracks that need to be detected in RWW operation. The third is the RWW error qualification threshold used for validation, which sets the minimum number of complete sync characters that must be detected in RWW mode to avoid setting the "lead sync error" status bit. To decide. Again, the first two values are
If the threshold does not cause too many temporary write errors, it is usually the same (eg 12) and the last value is higher because all tracks need to detect their sync characters. (Eg 16).

Block detection and validation are aided by three timeout periods. The first timeout starts at burst detection and PLL acquisition is delayed until the end of that timeout or 100% burst qualification is detected. This first timeout is used by deskew to delay PLL acquisition until all tracks should be burst. The second timeout starts at the beginning of PLL acquisition and ends when it is suspected that PLL acquisition across all tracks has occurred. RDF is the third after the acquisition of PLL is completed
Start the timeout of. It ends beyond the last time the sync character that caused the worst skew was detected. If the sync character qualification is not satisfied before the third timeout expires, then RDF assumes that the detected burst was not the first burst of the block. So RDF disables block processing and
Start a search for BG. If an IBG is detected before any of the three timeouts expires, the data flow disables block processing and looks for the burst again. In this way, RDF distinguishes between pseudo bursts and valid head bursts.

The advantage of providing programmable counts and qualification thresholds for detection and validation in RWW and "read-only" modes is the need for RWW operation known as "play-on-write (RWWA)". It becomes clear if the conditions are considered. The RWWA command instructs RDF to read one or more formatted blocks before the write format begins the write append. The "head of gap (BOG)" signal generated after the first block is read is used by the microcode to validate or adjust the write add point. If the first block is not detected using the canonical default value, the ERP (Error Recovery Procedure) will require the "read-only contiguous interval count threshold for IBG, and for IBG, burst and sync characters. It will attempt to read the block by dynamically reprogramming the "read only" track qualification threshold. If the "read ERP" finds the combination of threshold parameters needed to detect that block, the RWWA
The operation is started. RDF uses a "read-only" parameter to detect the first block, then
Switch the detection bank to the RWW parameters used to detect all subsequent blocks.

In summary, RDF nominally detects a single formatted block using the same detection criteria, regardless of the mode selected. But R
When validating a block during a WW operation or during an RWW operation known as RWWA, the portion of the format required for block detection is more well sorted by using various RWW threshold checks.
The results of these checks are reported to the microcode via the status register. The microcode can then decide whether to rewrite the block.

C. Read Data Flow Detection and Validation Logic Referring to FIGS. 2 and 3, a magnetic tape data storage device, or magnetic tape drive 30, is on a magnetic tape 34 formatted in the manner shown in FIG. Has one or a plurality of magnetic heads 32 for reading the data. In addition, tape drive 30 includes a tape drive control system having a programmable microprocessor (not shown) and a hardware-based block detection and validation system 36. The block detection / validation system 36 uses the magnetic read head 3
2 has a preamplifier and read detect circuit 38 of conventional design which receives the signal information from 2. The circuit 38 is shown in FIG. 2 as having 16 tracks on the tape 34. A preamplifier and read detect circuit 38 amplifies the signal received from the read head 32 and provides a data pulse output to a phase locked loop (PLL) circuit 40 and an asynchronous interblock gap and burst detect logic circuit (IBDT) 42. .

The IBDT circuit 42 is used in connection with IBG and acquisition burst detection and validation, while the phase locked loop circuit 40 is used in conjunction with sync character detection and validation. Both circuits are main state
Controlled by the machine 44. The main state machine 44 receives command and control information from a microprocessor command / decode register circuit 46 having one or more microprocessor storage registers. Main state machine 44 is preferably implemented as an application specific arrangement of combinatorial logic circuits having the configuration described by the state description below in more detail. State machine 44
Another embodiment includes a programmable logic array and a microprocessor based configuration.

The tape drive microprocessor, or main state machine, is responsible for various modes of operation of the tape drive 30 (eg, "read-only") including appropriate detection thresholds (and validation thresholds for RWW mode). , RWW) to provide a programmable threshold to a parameter and threshold circuit 48 containing a bank of microprocessor registers. Main state machine 44 determines which bank of threshold registers should be used for validation and detection during each mode. Block detect and validation status information is provided to the microprocessor via a block status circuit 50 that includes a holding latch and one or more microprocessor status registers configured to receive input from the holding latch. Will be returned.

The IBDT circuit 42 receives a 16-channel data pulse input from the preamplifier / read detect circuit 38 and provides selected data pulse intervals (eg, 101010 .... and 100000000100000000 ....). Logic circuitry is provided for identifying and counting and comparing the interval count with the programmable threshold stored in the parameter and threshold circuit 48. The IBDT circuit 42 uses the IBDT for each channel that meets the detection threshold criteria.
Prior to setting the G detect and burst detect latches, it is controlled by a programmed value in the parameter and threshold circuit 48 to detect a predetermined number of consecutive IBG and burst intervals.

FIG. 4 shows the IBDT that performs these functions.
Shows the components of the circuit. 16 channel data
The pulse input is provided to an interval counter circuit 52 which counts data pulse intervals.
The interval counter circuit 52 outputs the interval count value to the IBG detection / latch circuit 54, the burst detection / latch circuit 56, and the void detection / latch circuit 58 for each of the data pulse input lines of 16 channels. Output to. The detection / latch circuits 54 to 58 are
A comparator circuit is used to receive the parameter values from the microprocessor register bank of the parameter and threshold circuit 48 and compare those interval count values with the programmed interval count thresholds corresponding to the mode of operation being invoked. . For example, IBG
And burst detection and latch circuits 54 and 56, respectively, are programmable to set their detection latches when eight consecutive input signals are detected.
1 of IBG and burst detection and latch circuits 54 and 56
The 6 output channels correspond to the 16 data pulse input channels received from the preamplifier and read detect circuit 38. Each detect output channel goes high or low (ie, 1 or 0) depending on whether the required number of intervals have been detected and the corresponding output latch is set for that channel. The void detection / latch circuit 58 detects the occurrence of count overflow in the counter 52, which indicates the presence of a void area on the tape 34.

IBG and burst detection / latch circuit 54
And 56 include an RWW error latch that is initially set high before each detection sequence and cleared only when the appropriate "Play on Record (RWW)" error threshold is met. The RWW error threshold is provided by the parameter and threshold circuit 48. As above, RWW
The error validation threshold is preferably higher than a "read-only" or RWW detection threshold, which is often the same or substantially the same. The error latch is I
It provides 16 channel outputs used to generate BG and burst error signals, IBG error and burst error signals, respectively. The IBG error and burst error signals are generated when a predetermined number of IBG and burst detect latches are not cleared. This can be done by suitable track qualification circuitry, or preferably by logically ORing the outputs of each RWW error latch. It's 100% truck RWW
It is necessary to meet the RWW error threshold in the mode. This preferred embodiment is implemented by IBG error circuit 60 and burst error circuit 62. IB
The G error circuit 60 has suitable logic to generate the IBG error signal, and is preferably a logical OR circuit. Burst error circuit 62 has the same logic. As mentioned above, if one wants to change the number of tracks that can meet the RWW error threshold, it is also possible to use suitable qualification logic.

Referring to FIG. 2, there are three logic circuits 64, 66, and 68 used in detecting sync characters, IBG patterns, and burst patterns. Qualified logic is used to count the number of tracks reporting the detection signal. If the number of tracks to report matches or exceeds the qualification threshold provided by the microprocessor register bank in the parameter and threshold circuit 48, the qualification signal from the corresponding qualification logic will indicate it. . The qualification logic can be implemented using a carry lookahead adder that adds the number of tracks reporting the detected signal. A comparator compares this sum with a programmed qualification threshold that corresponds to the mode of operation being invoked.

Sync qualification logic 64 receives its 16 channel input from track logic 70 of FIG. The track logic circuit 70 produces a sync detect signal output from the clock and data inputs provided by the phase locked loop circuit 40. The track logic 70 is controlled by signals from the main state machine 44, including the track start signal and the force window signal, which are described in more detail below. The phase locked loop circuit 40 is controlled by the main state machine 44 via a 16 channel PLL acquisition signal which will be described in more detail below.

The IBG qualification logic circuit 66 is signaled by the IBG detection output from the detection latch of the IBG detection and latch circuit 54 and by the IBG qualification threshold from the parameter and threshold circuit 48. The burst qualification logic circuit 68 uses the burst detect output from the detect latch of the burst detect latch circuit 54 and the parameter threshold circuit 48.
Signal by the burst qualification threshold from.
IBG certified logic 66 and burst certified logic 68
The IBG certified output and the burst certified output are provided to the main state machine 44. Synchronized logic circuit 6
Sync state certified output from 4 is also the main state machine 4
4 is supplied.

The IBDT circuit 42 outputs the IBG error signal and the burst error signal to the block status circuit 5
0 in the block status circuit by supplying a holding latch at 0.
These signals are reported to the microprocessor via the status register. HOTI, which will be described in more detail below
The BG enabled signal is further supplied to the IBDT detection circuit 42.
Reported to the holding latch in the block status circuit 50, and then similarly provided to the tape drive microprocessor.

The main status machine 44 is I
BG reset, relaxation IBG, enable HOTIBG,
Burst reset, and controls the IBDT circuit 42 via five input lines represented as a relaxed burst.
The IBG reset line clears the IBG detection and latch circuit 54. The burst reset circuit clears the burst detection / latch circuit 56. The relaxed IBG line relaxes the IBG interval count threshold used by the IBG detection and latch circuit 54. The relax burst line relaxes the interval count threshold used by the burst detect and latch circuit 56. Enable H
The OTIBG signal increases the IBG interval count threshold used by the IBG detection and latch circuit 54.

The main state machine 44 is
The IBDT circuit 42 is controlled by switching between threshold register banks in the parameter and threshold circuit 48 via an input line represented as RWW mode select. The RWW mode select line programs the threshold parameter input provided to the IBDT circuit 42 from a "read only" threshold register bank to the RWW threshold register bank and vice versa. Additional circuitry used by the block detection and validation system 36 includes servo logic circuitry 72 and timer circuitry 74, both of which are described in further detail below.

D. Formatted Block Detection and Validation Referring to FIGS. 5-7, the main state machine 44 has serial combinatorial logic to perform the block detection and validation sequence beginning at state A. In the initial state A, the main state machine 44 waits for valid "command read" and "now read" signals from the servo logic circuit 72. This test occurs in process step 102. Main state
The machine must receive a valid read command, or a "now read" command will not cause a read operation. Before the "read command",
Microcode from the tape drive microprocessor will set the operating mode and all thresholds in the parameter and threshold circuit 48 to be used during the read operation. Furthermore, if the microcode does not give an initial threshold, a default threshold is given. The default good threshold is preferably sufficient to read multi-track (eg, 16-track) tapes.
However, in the hope of unforeseen problems, microcode is allowed to "fine tune" the behavior of logic circuits by varying various parameters.

Upon generation of a valid "read command" loaded by microcode, or upon generation of a "read now" signal from servo logic circuit 72, the main state machine will be in process step 104.
Proceed to. There, Main State Machine 44
Switches to the RWW parameter via the "RWW Mode Select" line when the RWW mode is programmed,
Therefore, the corresponding RW in the parameter / threshold circuit 48
The W threshold is selected for use. Therefore, the main state machine 44 uses the IBG detection / latch circuit 54.
, And proceed to state B. The condition is identified in FIG. 5 by reference numeral 106.

In state B, main state machine 44 begins looking for an IBG data pattern. The IBG detect indication is provided to the main state machine 44 by the IBG certified logic 66. The IBG certified logic circuit 66 uses the IBG detection line 42 in the IBG detection line.
The IBG detection display that arrives from is certified. As mentioned above, the IBG certification standard is programmable in the parameter and threshold circuit 48 by microcode and mode selectable (ie, programmable) by the main state machine 44. In process step 108, the main state machine is set to state A.
If the microcode does not generate a "TERMINATE" command to return to the main state,
The machine will wait indefinitely in the IBG detect state. If an IBG is detected in process step 110, the main state machine performs process step 112 to clear the burst detect and latch circuit 56 and the IB via the "burst mitigation" line.
The DT detection circuit 42 is set to the "detection burst mitigation" mode. So, the main state machine 44
Proceed to state C, indicated by reference numeral 114 in FIG.

In state C, the main state machine begins looking for a valid burst pattern. The burst detect indication is provided to the main state machine 44 by the burst qualification logic 68. The logic circuit 68
Qualifies the burst display arriving from the IBDT detection circuit 42 on the "burst detection" line. as mentioned above,
The burst certification standard can be programmed by microcode in the parameter and threshold circuit 48, and
Mode selectable (ie, programmable) by the state machine 44. The main state machine 44 waits indefinitely in a burst detect state until it finds a burst, or if the microcode does not issue a "done" command in process step 116 that causes the state machine to return to state A. To do.

When a burst occurs in process 118, main state machine 44 proceeds to process step 120 and performs a series of actions. First, the main state machine stores the state of the "IBG error" line in a holding latch in the block status circuit 50. The value of that latch is then read by the circuit 50.
Used to update the corresponding status bit in the microprocessor status register within. Therefore, the main state machine 44 resets the IBG detection and latch circuit 54, and further,
If the "BG detection mitigation" mode had previously been activated, it is terminated, so that the normal IBG detection threshold is restored according to the applicable operating mode. Finally, the main state machine 44 activates the timer circuit 74 to activate T1.
Start the timer, and then the process in FIG.
Transition to state D, shown as step 122.

In state D, the logic either waits for T1 to finish or for a "full track burst" indication.
The T1 timer is used for a predetermined number of data tracks, eg 1
00% of the tracks are in burst and end counting at the expected time when they are ready to acquire the PLL. If the T1 timer has not expired in process step 124, the main state machine
A test is performed to determine if a 00% burst qualification was received at process step 126. 1
If no burst qualification of 00 is obtained, then the logic tests in process 128 whether an IBG is detected. If an IBG is detected, it is assumed that the read head is reading the IBG, so the logic circuit will again be in state C to test for a burst.
Return to. If the T1 timer expires or a 100% burst qualification is obtained, the logic moves to process step 130 and begins bit synchronization. The main state machine activates the phase locked loop through the "PLL acquisition" line. So the T2 timer is started,
The main state machine moves to state E, shown by process step 132 in FIG.

In state E, in process step 134, the main state machine 44 waits for the T2 timer to expire. The T2 timer ends counting at the expected time required for the phase locked loop circuit 40 to obtain the clock acquisition. The time period is programmable by microcode and is given a default value if the time period is unprogrammed. If, in process step 136, an IBG is detected before the T2 timer expires, it is assumed that a spurious burst has occurred and the read head is still reading the IBG. Therefore, in process step 138, the main state machine turns off the "PLL acquisition" signal and resets the burst detect and latch circuit. Following the expiration of the T2 timer, the "PLL Acquire" signal ends and the "Track Start" and "Window Force" signals to the track logic 70 are activated. These signals initiate the track logic processing required to detect sync characters in order to obtain byte sync across those tracks. These actions are taken in process 140, at which time the T3 timer is started and the main state machine moves to state F, shown as process step 142 in FIGS.

In state F, the main state machine waits for the output of sync qualification logic 64 to determine if a sufficient number of tracks have detected their starting sync characters. The synchronization certification is process step 144.
Tested in. As mentioned above, the synchronization qualification criteria are programmable by microcode. When the T3 timer has not expired in process step 146 and no synchronization qualification is obtained in process step 144, the main state machine tests in process step 148 for the presence of the IBG. If it is detected, the main state machine returns to state C and begins looking for a burst as it is assumed that the read head is still reading the IBG. If the T3 timer expires before obtaining the required synchronization qualification, the main state machine will proceed to process step 150.
Move to, "Track start" signal and "Window forced"
De-energize the signal and return to state B to look for IBG. T
The 3 timer is used to allow a programmed number of tracks sufficient time to detect their sync characters.

If process step 144 receives a sync qualification detection, the main state machine moves to process step 152 and saves the burst RWW error condition reported by the "burst error" line. The signal is stored in a holding latch in the block status circuit 50. The main state machine also activates the "enable HOTIBG" line which raises the threshold for detecting IBG. This threshold is raised while a magnetic read head reads a block if one formatted block is partially overwritten by another block. IB
The GHOT threshold ensures that the detection logic reads a true IBG that is not a spurious low frequency data pattern in the current block. In process step 152, the main state machine activates the "IBG reset" line to reset the IBG detect and latch circuit 54. The main state machine then moves to state G shown in FIG. 6 as process step 154.

The main state machine remains in state G until the T3 timer expires at process step 156. If an IBG is detected, the "forced window" line is de-energized and the main state machine moves to state Y. In this state, the magnetic read head is still
Indicates that BG is detected.

When the T3 timer expires at process step 156, the main state machine moves to process step 162 to deactivate the "force window" line and restore the nominal burst detect threshold and format. Deactivate the "burst mitigation" line to prevent the detection of spurious burst signals in the marked blocks. Process step 162 is followed by regular block processing including termination of the block detection algorithm. Thereafter, the main state machine moves to state X, indicated by process step 164 in FIG.

In state X, the "IBG Relax" line is activated in process step 166 to relax the IBG detection threshold used by IBG detection and latch circuit 54 in preparation for the next IBG. The main state machine then transitions to state Y shown in FIG. 7 as process step 168.

State Y performs some housekeeping duty that occurs at the end of the block. State Y
Then, the main state machine performs process step 170. That process step 170
Includes disabling the track read circuit, resetting the IBG detect and latch circuit 54, storing IBGHOT in the holding latch of the block status circuit 50, disabling the "enable HOTIBG" line, and activating the T19 timer. The main state machine then moves to state Z shown in FIG. 7 as process step 172.

In state Z, the main state machine waits for the T19 timer to expire. It is used to identify one expected midpoint through the next IBG.
When this midpoint is obtained by the T19 timer of process step 174, the main state machine initiates process step 176. The main state machine stores the IBG error status in a holding latch in the block status circuit 50. In addition, it loads the information from its block status circuit holding the latches into the corresponding bit location in the microprocessor status register within that circuit 50, and then clears those holding latches. In other words, all status information from the previous block is reported to the microprocessor, so
Appropriate actions such as rewriting the block may occur based on its status value. Following process step 176, the main state machine tests in process step 178 for the "play-on-write (RWWA)" mode. Main state machine 4 when REEA mode is selected
4 activates the "RWW Mode Select" line in process step 180 to select the RWW register in the parameter and threshold circuit 48, thereby dynamically reprogramming its applicable threshold criteria. Following the RWWA test, in process step 182, the main state machine 44 tests for IBG. If IBG is not detected, process step 1
At 84, the IBG detection and latch circuit 54 is reset and the main state machine returns to state B to look for the IBG. I in process step 182
Assuming a BG is detected, the main state machine resets the IBG detection and latch circuit 54, resets the burst detection and latch circuit 56, sets the "burst mitigation" line, and goes to state C to look for a burst. Move. The aforementioned actions are taken at process step 186 in FIG.

It will be apparent from the above description that the detection and validation of the formatted block is performed by the tape drive microprocessor using slightly related hardware logic. Conveniently, various thresholds are programmable for IBG, acquisition burst, and sync character detection and validation. These thresholds include IBG interval counts, IBG qualification counts, acquisition burst interval counts, acquisition burst qualification counts, and sync qualification counts. "Read only" and "Playback during recording"
Programmable threshold banks are available for various modes such as. The threshold bank may have the same or substantially the same detection threshold for each mode when the "play-on-record" error validation threshold is used to ensure data write integrity in RWW mode. It is possible. The above system facilitates adjustment of the detection threshold "on the fly". These adjustments include the "IBG Relax" line, the "Burst Relax" line, and the "Enable HOT" line.
Given by the "IBG" line. Other threshold relaxation and strengthening operations can be implemented as needed.

[0058]

SUMMARY OF THE INVENTION An apparatus and method are provided for easily detecting and validating formatted blocks during read / write data operations in magnetic tape data storage systems.

[Brief description of drawings]

FIG. 1 is a graphical representation of a portion of a magnetic tape having formatted data blocks recorded on it.

FIG. 2 is a portion of a block diagram illustrating a magnetic tape drive that includes circuitry for detecting a formatted block on a magnetic tape and validating it.

FIG. 3 is another part of the block diagram of FIG.

FIG. 4 is a detailed block diagram showing a portion of the circuits of FIGS. 2 and 3.

FIG. 5 is the first part of a flow chart showing a method for detecting and validating formatted blocks on magnetic tape.

FIG. 6 is a second part of the flowchart of FIG.

7 is a third part of the flowchart of FIG.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G11B 20/10 341 Z 8322-5D 351 Z 8322-5D (72) Inventor Ricky W. Murray USA North Calle de Catalina, Tucson, Arizona 3370 (72) Inventor Susama Mehash Palanjape United States Arizona, Tucson, East Territory Drive 6000 (72) Fernando Quintana Arizona United States 10642 East Oakwood Drive, Tucson, PA

Claims (22)

[Claims] 1. Arranged in one or more tracks in the form of a series of formatted blocks on a magnetic tape medium in a plurality of modes including a read only (R) mode and a read-on-write (RWW) mode. A magnetic tape data storage system for reading and writing stored data, the method for detecting and validating the formatted block in association with a read / write data transfer operation comprising: (1) ) Detecting one or more formatted entity data patterns using one or more programmable detection thresholds that are the same or substantially the same in both the R mode and the RRW mode. And (2) in the RWW mode, 1 greater than each of the one or more programmable detection thresholds. Or determining if the format entity data pattern satisfies a plurality of RWW error validation thresholds, and (3) if the pattern does not meet the RWW error validation thresholds, data; Generating a status message indicating that block rewriting may be necessary. 2. The method of claim 1, wherein the detecting step detects interblock gap patterns, sync bursts, and sync characters. 3. The method of claim 1, wherein the programmable detection and validation thresholds include interval count thresholds. 4. The method of claim 1, wherein the programmable detection and validation thresholds include track qualification thresholds. 5. The step of detecting comprises dynamically changing one or more of the detection thresholds according to which format entity is being detected to raise or lower a detection criterion. The method of claim 1, wherein 6. One or more tracks arranged in the form of a series of formatted blocks on a magnetic tape medium in a plurality of modes including a read only (R) mode and a read-on-write (RWW) mode. A magnetic tape data storage system for reading and writing stored data, the method for detecting and validating the formatted block in association with a read / write data transfer operation comprising: (1) ) Detecting in the R and RWW modes a first data pattern representing an inter-block gap using a first programmable detection threshold, and (2) in the R and RWW modes, A step of detecting a second data pattern representing a block acquisition burst using a programmable detection threshold of 2. (3) detecting a third data pattern representing a forward sync character using a third programmable detection threshold in the R and RWW modes; and (4) in the RWW mode. , The first, second or third
Programmable R greater than each of the detection thresholds of
Determining whether a WW error validation threshold is satisfied by the first, second or third data pattern, and (5) indicating that a data block rewrite may be necessary. Generating a status message, and a method comprising. 7. The method further comprises relaxing the second detection threshold following detection of an inter-block gap, and recovering the second detection threshold following detection of the forward sync character. The method of claim 6 characterized. 8. The step of increasing the first detection threshold following detection of a sync character and the step of recovering the first detection threshold following detection of a data block. Item 6. The method according to Item 6. 9. A method comprising: relaxing the first detection threshold following detection of a formatted block; and recovering the first detection threshold following detection of the interblock gap. The method of claim 6 characterized. 10. The first and second detection thresholds include an interval count threshold corresponding to the number of repeating intervals of the interblock gap and the pattern of acquired burst characters, and the third detection threshold is a synchronization character. 7. The method according to claim 6, wherein the track qualification threshold value corresponds to the number of tracks that are simultaneously detected. 11. A second representing the block acquisition burst.
A first programmable time period for performing the step of detecting a data pattern of and a third data representing the forward sync character subsequent to the end of the first programmable time period. The method of claim 6, further comprising the step of detecting a pattern. 12. A second programmable time period for obtaining a clock acquisition over all data tracks, and a second representation of said forward sync character following the end of said second programmable time period. 12. The method of claim 11, further comprising the step of detecting 3 data patterns. 13. A third step for performing a step of detecting a third data pattern representing said forward sync character.
13. The method of claim 12, wherein the programmable time period is provided. 14. A second representing the block acquisition burst.
Detecting the data pattern of the inter-gap characters and detecting the third data pattern representing the forward sync character, testing for the presence of repeated character patterns representing inter-block gaps, and the characters of the inter-block gaps. 7. The method of claim 6, returning to the step of detecting a second data pattern representative of the block acquisition burst if a pattern repeat is detected during the test. 15. Arranged in one or more tracks in the form of a series of formatted blocks on a magnetic tape medium in a plurality of modes including a read only (R) mode and a read-on-write (RWW) mode. A magnetic tape data storage system for reading and writing stored data, the method for detecting and validating the formatted block in association with a read / write data transfer operation comprising: (1) ) A first representing an inter-block gap using first and second programmable detection thresholds that are the same or substantially the same in both the R and RRW modes.
And (2) detecting a block acquisition burst using third and fourth programmable detection thresholds that are the same or substantially the same in both the R and RRW modes. Detecting a second repeating data pattern to represent, and (3) using a fifth and sixth programmable detection threshold that is the same or substantially the same in both the R and RRW modes. Detecting a third repeating data pattern representing a directional sync character, and (4) in the RWW mode, setting the RWW error validation threshold greater than each of the first to sixth thresholds to the first, Determining if a second or third repeating data pattern is satisfied, (5) said first, second or third repeat Generating a status message indicating that the data block may need to be rewritten when the returned data pattern does not meet the RWW error validation threshold. 16. One or more tracks arranged in the form of a series of formatted blocks on a magnetic tape medium in a plurality of modes including a read-only (R) mode and a read-on-write (RWW) mode. A magnetic tape data storage system for reading and writing stored data, the detection and validation system for detecting and validating the formatted block in connection with read and write data transfer operations. The detection and validation system includes: (1) one or more programmable R and RWW thresholds and the R and RWW thresholds that are the same or substantially the same in both the R and RRW modes. A storage resource containing one or more programmable RWW error thresholds that are greater than the corresponding RWW thresholds. , In the (2) interval count threshold logic circuit,
(A) a first input for receiving one or more input values representing a formatted entity data pattern, and (b) one or more from the storage resource representing the programmable threshold. A second input for receiving an input value, and (c) an output for generating one or more output values representative of the format entity detection signal and the validation signal, and (3) ) A track qualification threshold logic circuit comprising: (a) a first input for receiving one or more input characters representing the format entity detection signal, and (b) the storage resource representing a programmable threshold. A second input for receiving one or more input values of, and (c) one or more output values representing the format entity track qualification signal. And (4) a state machine for controlling the operation of the interval count threshold logic circuit and the track board threshold logic circuit. Storage system. 17. The magnetic tape data storage device of claim 16, wherein the interval count threshold logic circuit includes an IBG detection circuit and a burst detection circuit. 18. The magnetic tape of claim 16, wherein the track qualification threshold logic circuit includes a sync character qualification circuit, an IBG qualification circuit, and a burst qualification circuit.
Data storage device. 19. The magnetic tape data storage device of claim 16, wherein the state machine includes an output for providing a threshold programming signal to the storage resource. 20. The magnetic tape data storage device of claim 16, wherein the state machine includes an output for providing a threshold relaxation signal and a threshold enhancement signal to the interval count threshold logic circuit. . 21. One or more tracks arranged in the form of a series of formatted blocks on a magnetic tape medium in a plurality of modes including a read only (R) mode and a read-on-write (RWW) mode. A magnetic tape data storage system for reading and writing stored data, the method for detecting and validating the formatted block in association with a read / write data transfer operation comprising: (1) ) One or more format entity data data using storage resources including a first bank of programmable thresholds corresponding to the R mode and a second bank of programmable thresholds corresponding to the RWW mode. A step of detecting a pattern, and (2) a program of the first bank according to an operation mode of the magnetic tape medium. A step for selecting a programmable threshold grayed possible threshold or the second bank, the method more comprising. 22. The first bank of programmable thresholds and the second bank of programmable thresholds include substantially the same R threshold and RWW threshold, and the second bank of programmable thresholds includes the R threshold. Threshold and R
One or more Rs that are higher than the corresponding thresholds of the WW threshold
22. The method of claim 21, including a WW error threshold.